The present invention relates to a chip capacitor required to have a large vibration resistance, and particularly to an aluminum electrolytic chip capacitor to be mounted on a board as a surface-mounted capacitor.
FIGS. 16(a) and 16(b) are a front sectional view and a side sectional view of a conventional aluminum electrolytic chip capacitor, respectively. Aluminum electrolytic chip capacitor 21 (hereinafter called capacitor 21) includes a capacitor element 23, an open-bottomed cylindrical metal case 24 in which the element 23 and electrolyte for driving are accommodated, and a sealing member 25 for sealing the open end of case 24. The capacitor element 23 is formed by winding anode foil and cathode foil (not shown) with an anode lead wire 22a and a cathode lead wire 22b connected thereto, respectively, with a separator disposed between them. A shrink portion (reduced-diameter portion) 24a is formed at sealing of the case 24.
An insulated terminal plate 26 is disposed so as to abut the open end side of case 24, and its outer surface (a bottom of the figure) has holes 26a and groove portions 26b. Through the holes 26a, the lead wires 22a and 22b led out of capacitor element 23 pass, and in the groove portions 26b, the lead wires 22a, 22b bent perpendicularly are placed. The bent portions of lead wires 22a, 22b are finished flat. In this manner, the capacitor 21 is mounted on a surface of a board (not shown).
After the conventional capacitor is mounted on the board, when a strong stress of vibration is applied thereto in the Y direction perpendicular to the X direction, i.e., the direction of connecting the lead wires 22a and 22b as shown in FIG. 17, the capacitor 21 vibrates like a pendulum since it is connected to the board only at two portions of the lead wires 22a and 22b. Accordingly, soldered portions of the lead wires 22a and 22b connected to the board are peeled off, which may cause breakage of the lead wires.
Another conventional capacitor includes an insulated terminal plate of housing-like shape surrounding a capacitor body with lead wires connected thereto. In this technology, it is necessary to make the outer diameter of the body substantially identical to the inner diameter of a housing portion of the terminal plate in order to improve the vibration resistance. Therefore, it is difficult to mount the capacitor body in the housing portion.
Japanese Patent Laid-Open No.9-162077 discloses a support portion that rises and extends from a periphery of an insulated terminal plate, and a projection disposed at the support portion which fits in a shrink groove portion of a capacitor. This document further discloses a capacitor including a support portion split by notches, and a capacitor including a cylindrical support portion made of resin having elasticity unitarily formed with an insulated terminal plate. These capacitors, since their support portions have annular shapes, have their capacitor bodies mounted. Since the support portions are formed only up to the shrink groove portions, these capacitors cannot stand sufficiently against vibrations in consideration of mounting in, for example, automobiles.
As shown in FIG. 18, when being bent along the groove portion 26b disposed in the insulated terminal plate 26, the lead wires 22a and 22b are bent at acute angles only at one portion of each hole 26a. Therefore, the lead wires 22a and 22b, once bent and placed in the groove portions 26b, tend to return to their original positions due to a spring-back effect of the bent portions, and thereby generate a float t. The float t lowers soldering strength when a thin solder is applied.
Further, as shown in FIG. 19, in a capacitor including a dummy terminal 28 disposed on the outer surface (soldering surface or bottom surface) of the insulated terminal plate 27, the above problem is particularly remarkable. In the worst case, the solder does not contact with the dummy terminal 28. This may lead particularly to a serious problem since a thinner solder has been used recently.
In order to solve such problem, the lead wires 22a are 22b are bent with stronger forces, or the groove portions 27a in the insulated terminal plate 27 are formed deeper, thereby coping with the spring-back effect. However, such measure may invite a problem that the lead wires 22a and 22b cannot be soldered since they remain deep in the groove portions 27a. 
An aluminum electrolytic chip capacitor is easily mounted, has an excellent vibration resistance, and can be soldered reliably even if a lead wire is positioned deeply in a groove portion formed in an insulated terminal plate.
The capacitor includes a capacitor element including a lead wire for leading to the exterior, a metal case for accommodating the capacitor element, a sealing member to seal an open end of the metal case, and an insulated terminal plate disposed so as to abut the sealing member. The metal case has a shrink portion of annular shape formed at the sealing. The capacitor further includes a wall portion disposed at a position other than on a line in a lead wire bending direction of a periphery of the insulated terminal plate. The wall portion is equal to or higher than the height of the shrink portion, and has its inner surface abut and hold the periphery of the metal case.
The capacitor, upon being mounted on a board, stands strong against vibrations given in all directions including a direction crossing the lead wire bending direction, thereby assuring excellent reliability.